This invention pertains to conveyor sortation systems and, in particular, to a method and apparatus for inducting product to a sorter, wherein the sorter includes a continuous conveying member defining a plurality of transport positions and a plurality of sort destinations for receiving product discharged from the continuous member. The invention has application to both linear sorters, such as positive displacement sorters, and carousel sorters, such as tilt-tray and cross-belt sorters.
The quintessential goal for any material-handling system is to maximize the throughput of product through the system. In the case of a sorter, it is known that the throughput of the sorter is limited by the ability of the system to induct product to the sorter at a rate that matches the throughput of the sorter, with adequate gaps between the product. If an insufficient rate of product is supplied to the sorter, then the sorter becomes starved and is incapable of meeting its rated throughput.
A common technique for keeping the sorter supplied with product is to build accumulation into the system upstream of the induct. With a backlog of product at the input to the induct, the function of the induct becomes limited to ensuring that adequate product gaps are developed and, in the case of multiple-line inducts, that the products are merged together from the multiple lines. However, accumulation comes at a cost and is not always feasible. For example, some systems require that substantially all of the conveyors be of the belt variety. This is especially common in the parcel-handling industry where packages may be poorly packaged and may include protruding items from the packages. The use of live-roller conveyors, which are the common form of accumulation, is considered to be inappropriate for handling such parcels. Accordingly, the ability to induct product to the sorter at an adequate rate becomes difficult when accumulation upstream of the sorter is not practical, such as where the conveyors are of the belt variety.
Carousel-type sorter systems are known to be able to handle product of a wide range of characteristics and can be compact and configured in many different ways. In particular, the induct systems and the destination chutes, or conveyors, can be arranged at any place along the carousel and can be arranged on one or both sides of the carousel. In order to provide maximum product throughput with a carousel sorter, empty units are booked, or reserved, for product positioned on the induct. However, a particular timing window must exist in order to accelerate the product to the speed of the carousel to meet the booking requirement for a particular empty carrying unit. If this window cannot be met, it is necessary for the carrier to pass by the induct without a product being loaded on that unit. It should be apparent that the more carriers that pass by the induct without receiving a product, the lower the throughput of the carousel-type sortation system. Conversely, the throughput of a carousel-type sorter can be increased by ensuring a maximum loading of the carriers passing by an induct.
The present invention provides a sortation system and a method of inducting to a sortation system which increases the performance of the sorter by ensuring an improved supply of product to the sorter.
A sortation system and method of inducting product to a sorter, according to an aspect of the invention, is useful with a sorter having a continuous member defining a plurality of transport positions of the continuous member and a plurality of sort destinations for receiving product discharged from the continuous member. An induction system is provided that includes at least one induction unit having a receiving end for receiving product from a product source and a discharge end for discharging product to the continuous member. The at least one induction unit includes a plurality of tandem-conveying units between the receiving end and the discharge end and a control controlling the conveying units. According to this aspect of the invention, the at least one induction unit follows a speed of the continuous member. This includes starting substantially as soon as the continuous member is moving and decreasing in speed substantially only when the continuous member decreases in speed.
This aspect of the invention allows an induction system which does not require accumulation upstream of the induction system. Furthermore, bookings of product on the induction unit can be maintained, notwithstanding variation in speed of the continuous member.
A sortation system and method of inducting product to a sorter, according to another aspect of the invention, is useful with a sorter having a continuous member defining a plurality of transport positions of the continuous member and a plurality of sort destinations for receiving product discharged from the continuous member. An induction system is provided having at least two induction units. Each of the induction units has a receiving end for receiving product from a product source and a discharge end for discharging product to the continuous member. The sorter further includes a control which determines gap between product that will be discharged to the continuous member. The induction unit is capable of discharging product to the continuous member irrespective of the gap between product.
This aspect of the invention also facilitates the ability of the induction unit to follow the speed of the continuous member because it is not necessary to shut down the induction unit when a product having an improper gap is detected. Rather, the product with the improper gap may be discharged to the continuous member and either sorted to a special lane or recirculated to the induction subsystem.
A sortation system and method of inducting product to a sorter, according to another aspect of the invention, is useful with a sorter including a continuous member defining, a plurality of transport positions of the continuous member and a plurality of sort destinations for receiving product discharged from the continuous member. An induction system is provided having at least one induction unit with a receiving end for receiving product from a product source and a discharge end for discharging product to the continuous member. The at least one induction unit includes a plurality of tandem conveying units between the receiving end and a discharge end and a control for controlling the conveying units. According to this aspect of the invention, the control books at least one transport position for receipt of product from the at least one induction unit. The control books a transport unit for a product when that product is at a booking conveying unit and adjusts relative spacing between a product and the respective transport position booked for that product on the conveying units downstream of the booking conveying unit.
This aspect of the invention allows multiple product to be booked on the at least one induction unit and awaiting discharge to the continuous member. Furthermore, by booking the transport position for a product at an upstream portion of the at least one induction unit enhances the ability of the induction system to ensure an acceptable gap between the products discharged to the continuous member.
A sortation system and method of inducting product to a sorter, according to another aspect of the invention, is useful with a carousel sorter having a plurality of product carriers arranged in an endless loop and a plurality of sort destinations for receiving product discharged from the carriers. An induction system is provided having at least one induction unit with a receiving end for receiving product from a product source and a discharge end for discharging product to the carriers. The sortation system further includes a control for monitoring product on the carriers and booking carriers for product on the induction system. The control is capable of booking carriers irrespective of whether the carriers are already carrying product.
This aspect of the invention facilitates the booking of carriers well in advance of the induction system, thereby increasing the number of carriers that can be booked at the induction system. If a carrier that is carrying a product is booked, but is unable to discharge its product prior to arriving at the induction system, the booking may be cancelled.
These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.